If it doesn't lose strength, Hurricane Katrina will become only the fourth Category Five storm to hit the United States since record-keeping began.
The last was 1992's Hurricane Andrew, which leveled parts of South Florida, killing 43 people and causing $31 billion in damage.
The other Category Five storms were the 1935 Labor Day hurricane that hit the Florida Keys and killed 600 people; and Hurricane Camille, which devastated the Mississippi coast in 1969, killing 256.
Katrina formed in the Bahamas and ripped across South Florida on Thursday as a Category One storm before moving into the Gulf of Mexico.
Water surface temperatures in the Gulf are as high as 90 degrees -- high-octane fuel for hurricanes.